1. Field of the Invention
The present invention is related to an extensional module, and more particularly to an extension interface module which can amplify and enhance signal and then output the amplified and enhanced signal.
2. Description of Prior Art
The universal serial bus (USB) transferring interface has an advantage of supporting hot swapping, (namely, plug-and-play), more particular, many electronic devices such as keyboard, mouse, portable hard driver and webcam are connected to computers through the USB transferring interface for convenient using. USB transferring interface is becoming a most popular transferring interface of computer.
However, a main board of a computer has just a fixable allocation space for disposing limited amount of USB ports. When users have too many devices having USB port, the USB port will be inadequate. Moreover, in most of computers, the USB ports are located at a back-end of the computer, thus, it is inconvenience for users during plugging and pulling the USB devices.
As described above, an expansion interface was disclosed, such as lead lines of the computer, as shows in FIG. 1, which is a perspective view of conventional USB lead line. The lead line 1 is an integrated circuit board, which is integrated with a head phone jack 11, a microphone jack 12 and a USB connector 13 into a circuit board, and the circuit board is electrically connected to a main board through a cable 14.
However, some USB devices, such as flash drives, are directly connected to the USB connector 13 of the lead line 1 through USB plug, and the others, such as portable optical disk drive or portable hard drive, are connected to the USB connector 13 of the lead line through an external transmission line (or called extended line). The cable 14 of the lead line 1 has a predetermined length. The sum length of the cable 14 and the extended line will exceed the standard transmission distance of USB when the extended line is over length. And the length of the cable 14 or the expended line will exceed the standard transmission distance when the lead line 1 is poorly designed or using a special requirement with very long expended line. Therefore, the signal or data delivered from the main board will be attenuated, damaged or lost in the transfer process during the over-length of transferring distance. In the situation said above, the lead line does not have to need to be used.
Furthermore, the USB transmission interface has been developed to USB 3.0, and the transmission rate is raised to 5 Gbps from 480 Mbps of USB 2.0. The specifications of USB 2.0 are no longer applicable when the transmission rate has been raised. As a result, signal attenuation, damage and loss in the high transmission rate might occur.